Epoxy resins in use today are limited by the ability to form a dispersion in water. It is highly desirable to have epoxy resins available in a form that is water stable and can be easily dispersed in water. Further, it is desirable to disperse the epoxy resins without the requirement of ionic or salt components such as carboxylic acids or amine salts that damage or corrode inorganic surfaces such as metal and glass. Also, it is desirable to avoid the use of dispersing aids such as nonionic, anionic, and cationic surfactants, since these surfactants interfere with the film forming properties of the epoxy resin. Furthermore, the avoidance of organic solvents is desirable because it reduces volatile organic compound emissions to the workplace and the environment and provide greater safety in the workplace because of reduced flammability and toxicity during production. Hence, there is an on-going need to provide epoxy resins that are easily dispersed in water.
Common uses for these dispersions of epoxy resins are as ingredients in coatings for inorganic surfaces, such as siliceous materials, metals or metal oxides and in adhesives. Coatings produced from dispersions of epoxy resins are used to protect the surface from abrasion and corrosion.
A typical use for these dispersions of epoxy resins is as ingredients in glass fiber coatings, often referred to as "sizes". Glass fibers are produced by melting glass in a furnace and allowing it to flow through small holes in a platinum/rhodium plate usually referred to as a bushing. After the molten glass passes through the holes it is cooled and drawn onto a collecting device at a very high rate of speed. During this process, there is considerable glass-to-glass abrasion or friction which can cause significant weakening of the glass fibers. To protect the glass fibers from abrasion, a sizing composition is applied to the glass fibers using an applicator as the fibers are drawn and before they are wound on the collector. These dispersions of epoxy resins also impart other desirable properties to the glass fibers, such as binding or gluing the individual fiber filaments into a fiber strand, improving fiber handling or processing to make a fiber reinforced plastic composite or improving the wetting out of the fiber with the resin that is used to make a composite.
In the fiber glass art a size that is water based is generally preferred because of its ease of application to glass fibers as well as the greater safety associated with lower flammability and absence of volatile organic components.